Q:
Could you tell me what the scale is in the X-ray picture of Eta
Carinae? And is the angular range the same in all the " first
target" pictures?

A:
For each First Chandra Image multi-wavelength gallery, there is
an accompanying piece entitled "What Do These Images Tell Us."
In those write-ups, you will find the scale for the objects. For
example, Eta Carinae's "Images not to scale" statement links
directly to http://chandra.harvard.edu/photo/0099/what.html
which has the scale listed under each object's thumbnail.